tures. In a large randomized trial in over 3,000 elderly retirement home residents (mean age 84 years), daily supplementation with 1,200 mg (30 mmol) of calcium and 20 µg (800 IU) of vitamin D reduced hip fracture and other nonvertebral fracture rates (Chapuy et al., 1992). In a randomized trial in younger men and women (aged 65 and older, mean age 71 years) residing at home, supplementation with 500 mg (12.5 mmol) of elemental calcium and 8.8 µg (352 IU) of vitamin D significantly reduced nonvertebral fracture rates (Dawson-Hughes et al., 1997). Notably, the men and women in this study had estimated usual dietary calcium and vitamin D intakes of 750 mg (18.8 mmol) and 5.0 µg (200 IU), respectively. Two other studies have assessed the effect of calcium alone on fracture rates (Chevalley et al., 1994; Recker et al., 1996). Among women with low usual daily calcium intakes (mean 450 mg [11.3 mmol]), calcium supplementation (1,200 mg [30 mmol]/day) reduced the vertebral fracture rate in women with prior vertebral fractures, but it did not reduce the risk of first vertebral fractures (Recker et al., 1996). In contrast, a reduction in first vertebral fractures with calcium supplementation of 800 mg (20 mmol)/day has been noted (Chevalley et al., 1994). Although these studies point to a favorable effect of calcium, additional studies are needed to estimate the magnitude of the impact of calcium intake on fracture rates. Available data do not allow use of fracture outcomes to identify the AI for calcium.